Integrated-optic spectrometer and method

ABSTRACT

An integrated-optic spectrometer is disclosed for analyzing the composition of light reflected off a sample under analysis. In a simplified embodiment, the spectrometer includes a buffer, located on the top of a substrate, which is etched to create a diffraction grating having grating lines. The diffraction grating and grating lines are formed to provide diffraction of discrete wavelengths of light, while providing for maximum transmission of non-diffracted wavelengths. A waveguide is fabricated on top of the etched buffer through which the reflected light is directed. A photodiode detector array is located above the waveguide into which the diffracted wavelengths are diffracted, providing an analysis of the composition of the reflected light. A clad encompasses the integrated-optic spectrometer, thereby providing protection from outside interference.

FIELD OF THE INVENTION

The present invention generally relates to a system for analyzing light.More specifically, the invention is related to an integrated-opticspectrometer and method for guiding an inputted light source anddiffracting discrete wavelengths from the guided light for compositionanalysis, by use of successive diffraction gratings.

BACKGROUND OF THE INVENTION

A spectrometer is generally any device that produces a spectrum by thedispersion of light and is calibrated to measure transmitted energy orradiant intensities with respect to wavelengths of radiation. Said in adifferent way, a spectrometer is a photometer for measuring the relativeintensities of light in different parts of a spectrum.

Spectrometers are used in numerous different industries. Examples ofsuch industries include the automotive industry, for identifying certainpaint or pigment compositions, thereby making possible the applicationof a matching paint; the textile industry, for ensuring the consistencyof color from one dye lot to the next; and the cosmetic industry, foridentifying the facial properties of a consumer, thereby allowing theidentification of cosmetics which will enhance these facial properties.

Spectrometers utilized for these and other purposes typically utilize adiffraction grating which may be either curved or flat, to disperse thelight into a spectrum. The diffracted light intensity at each wavelengthis then measured by a suitable detector, such as a photodiode detectorarray or a photomultiplier tube.

While current spectrometers are effective in analyzing the opticalproperties of certain samples, they are generally costly, bulky, andheavy. Therefore, there is a need in

SUMMARY OF THE INVENTION

In the context of this document, “integrated-optic” refers to a deviceor devices, fabricated on or in an optical waveguide by any process ormethod for producing micromachined or micro-level structures, including,but not limited to, disposition techniques (e.g., sputtering,evaporation, screen printing, etc.), microlithography, holegraphy, orthin-film fabrication techniques.

Briefly described, the invention is an integrated-optic spectrometerwhich utilizes the combination of a waveguide, fabricated onto anoxidized substrate, which has an array of diffraction gratings and adetector array, capable of analyzing discrete wavelengths, which ismounted on the waveguide so as to receive the light of differentwavelengths diffracted by the grating array. The diffraction gratingseach comprise a series of grating lines and are constructed to providefor optimal transmission of wavelengths not diffracted by thediffraction grating. Therefore, the inputted light is guided through thewaveguide and discrete wavelengths are diffracted by the diffractiongratings onto the photodiode detector array which in turn measures theintensity of the light at the discrete wavelengths for determiningcomposition, while optimally transmitting non-diffracted wavelengthsthrough the waveguide.

In general, the architecture of a first embodiment of the inventioncomprises a single layer waveguide. The surface layer of a substrate isfirst oxidized, creating a buffer layer. This buffer layer is theneither etched by a technique such as holographic or microlithographictechniques, or otherwise fabricated upon, thereby creating diffractiongratings. A waveguide is then fabricated onto the buffer layer creatinga path through which the light to be analyzed may travel. A clad layeris then fabricated to encompass the waveguide and gratings, therebyproviding protection to the waveguide and hampering interference fromoutside elements. Finally, a suitable detector array is mounted on theclad layer so as to measure the intensity of the wavelengths diffractedby each grating in the array. Depending on the desired field ofapplication, the diffraction gratings may be designed to diffract theselected wavelength of light either within the plane of the waveguide,but in a different direction from the inputted light, or out of plane ofthe waveguide.

A second embodiment of the present invention utilizes a bi-layerwaveguide. This embodiment comprises a first layer of waveguidefabricated onto the oxidized surface layer of a substrate, or bufferlayer, a second buffer layer fabricated onto the top of the firstwaveguide layer, a grating structure etched or otherwise fabricated ontothe second buffer layer, thereby fabricating the grating structure, asecond waveguide layer fabricated onto the top of the second bufferlayer, and a clad layer fabricated on top of the second waveguide layer.A suitable detector array is then mounted either on top of the clad oralong its side, as described previously. Fabricating the diffractiongratings on, or in, the second buffer layer of this embodiment maximizesthe intensity of the diffracted light due to the location of thediffraction gratings between the first and second waveguide layers.Because the second buffer layer in quite thin, as compared to the twowaveguide layers, this multi-layer system functions as a single thickwaveguide with gratings embedded in or near its center.

Optionally, the integrated-optic spectrometer may be equipped withnumerous diffraction gratings constructed in succession. Both of theabove-mentioned embodiments utilize diffraction gratings which areconstructed to provide for optimal transmission of wavelengths tosuccessive diffraction gratings, after the diffraction of discretewavelengths by preceding diffraction gratings. Therefore, successivediffraction gratings are provided for while providing an accurateanalysis of the diffracted light by the detector array.

The invention has numerous advantages, a few of which are delineatedhereafter, as examples. Note that the embodiments of the invention thatare described herein possess one or more, but not necessarily all, ofthe advantages set out hereafter.

One advantage of the invention is that it may be utilized in a multitudeof industries due to its low weight, and small size.

Another advantage of the invention is that it may be implemented on asingle chip, thereby decreasing cost and making possible the fabricationof hand-held battery powered devices, incorporating the invention.

Another advantage of the invention is that it allows for multiplediffraction gratings to be utilized in succession while preventing eachsuccessive diffraction grating from distorting non-diffractedwavelengths which pass through the waveguide.

Another advantage is that the second embodiment provides for a thickerwaveguide since two waveguide layers are used. Therefore, a largerreflected light source may be analyzed, and the inputted light may bemore easily coupled into the waveguide.

Another advantage provided by the second embodiment is that it providesdiffraction gratings at the peak of the guided mode intensities,insuring strong interaction with the gratings.

Other objects, features, and advantages of the present invention willbecome apparent to one with reasonable skill in the art upon examinationof the following drawings and detailed description. It is intended thatall such additional objects, features, and advantages be included hereinwithin the scope of the present invention, as defined by the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be more fully understood from the detaileddescription given below and from the accompanying drawings of thepreferred embodiments of the invention, which, however, should not betaken to limit the invention to the specific embodiment, but are forexplanation and for better understanding only. Furthermore, the drawingsare not necessarily to scale, emphasis instead being placed upon clearlyillustrating the principles of the invention. Finally, like referencenumerals in the figures designate corresponding parts throughout theseveral views.

FIG. 1 shows a representative diffraction grating in accordance with thepresent invention.

FIG. 2 shows a cross-section of an integrated-optic spectrometer inaccordance with a first embodiment of the present invention.

FIG. 3 shows a cross section of an integrated-optic spectrometer inaccordance with a second embodiment of the present invention.

FIG. 4 shows a cross-section of diffraction gratings utilizing negativegrating lines for utilization in the spectrometers represented by FIGS.2 and 3.

FIG. 5 shows a cross-section of diffraction gratings utilizing positivegrating lines for utilization in the spectrometers represented by FIGS.2 and 3.

FIG. 6 depicts the diffraction and transmission of an inputted lightsource in a side view of the integrated-optic spectrometer havingselected wavelengths diffracted out of the plane of the waveguide, inaccordance with the first and second embodiments of the invention.

FIG. 7 depicts the diffraction and transmission of an inputted lightsource in the integrated-optic spectrometer in accordance with the firstand second embodiments of the invention, wherein a stand-off layer isutilized between the waveguide and the detector array.

FIG. 8 depicts the diffraction and transmission of an inputted lightsource in a top view of the integrated-optic spectrometer in accordancewith the first and second embodiments of the invention, having gratinglines designed to diffract light of selected wavelengths at a specifiedangle within the plane of the waveguide.

FIG. 9 depicts the diffraction and transmission of an inputted lightsource in the integrated-optic spectrometer in accordance with the firstand second embodiments of the invention, having grating lines designedto diffract light of selected wavelengths at an angle more or lessperpendicular to the plane of the waveguide.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows a diffraction grating 10 for utilization in anintegrated-optic spectrometer 14 (FIG. 6) in accordance with the presentinvention. In accordance with the invention, the diffraction grating 10is formed to diffract discrete wavelengths from incident light, whileproviding for optimal transmission of the wavelengths which are notdiffracted. A series of grating lines 12 are formed on the diffractiongrating 10 and perform the actual diffraction of the incident light. Inaccordance with the first or second embodiments of the invention, forexample, the diffraction grating 10 may be in the form of a 30°parallelogram with the individual grating lines at an angle of 45° tothe direction of propagation of incident light within the waveguide.These specifications for the diffraction grating 10 and grating lines 12are ideal due to their providing for optimal diffraction of discretewavelengths within the plane of the waveguide, while also providing foroptimal transmission of non-diffracted wavelengths. As shall be furtherexplained below with reference to FIG. 2, the diffraction provided forby these specifications occurs such that the light of the selectedspecifications remains within the waveguide but is coupled out of theoriginal light path at approximately right angles to the originaldirection of light propagation.

It will be appreciated by those reasonably skilled in the art thatdiffraction grating 10/grating line 12 combinations having differentspecifications (different shaped diffraction grating 10 and a differentangled grating lines 12) may be utilized to provide an effect similar tothat provided by the 30° parallelogram, however, the diffraction andtransmission performed by such combinations may not prove to be asoptimal in nature. For example, in an alternate embodiment, thediffraction grating 10 may be in the shape of a square or a rectanglewith the grating lines 12 at right angles to the direction ofpropagation of light within the waveguide, such that light is coupledout of the wave guide in a direction more or less perpendicular to theplane of the waveguide.

The size and spacing of the individual grating lines 12 determine whichdiscrete wavelengths are diffracted by the diffraction grating 10. It isdue to the form of the diffraction grating 10, and the grating lines 12therein, that light may have certain discrete wavelengths diffracted bythe diffraction grating 10, while allowing other wavelengths of thelight in the waveguide to be transmitted with minimal interference. Asan example, for the short wavelengths of blue light to be diffracted,the grating lines 12 must contain a very narrow space between eachgrating line. Therefore, the diffraction grating 10, with encompassingnarrow grating lines 12, will diffract the shorter wavelengths, whileallowing longer wavelengths to be optimally transmitted through thewaveguide. Similarly, for the longer wavelengths of red light to bediffracted, the grating lines 12 must have a wider space between eachgrating line. Therefore, a different diffraction grating 10 withencompassing wider grating lines 12 will diffract longer wavelengthswhile allowing other wavelengths (both longer and shorter) to beoptimally transmitted through the waveguide.

FIG. 2 shows an integrated-optic spectrometer 14 in accordance with thefirst embodiment of the invention. For fabrication of theintegrated-optic spectrometer an optically flat surface of silicondioxide (SiO₂), is formed on the top surface of a suitable substrate 20creating a buffer layer 22 thereupon. As an example, if the substrate 20is formulated from glass or quartz, the buffer layer 22 is formed bysimply polishing the substrate 20. As another example, if the substrate20 is fabricated from silicon, the silicon dioxide buffer layer 22 canbe grown thermally or deposited by sputtering or other techniques.

In the first embodiment, the substrate 20 is made of silicon and,therefore, after thermal oxidation, the buffer layer 22 is SiO₂. Asmentioned above, alternate materials which may be utilized informulating the substrate 20, including, but not limited to, fusedquartz or optical glass. Silicon, however, is the preferred substratematerial due to its atomically flat surface and its dark compositionand, therefore, its absorbing characteristics. While fused quartz,optical glass, and silicon have been used as examples of materials whichmay be used for formulating the substrate 20, one of ordinary skill inthe art will appreciate that any material with characteristics similarto silicon dioxide may be used.

A diffraction grating 10 is etched into the buffer layer 22 using, forexample, photolithography. This etching leaves a negative grating linestructure, as shown in FIG. 4, through which the reflected incidentlight is diffracted. As previously mentioned, the grating lines 12 maybe constructed to be at an angle of 45° with the vertical plane of thewaveguide. Alternatively, the diffraction grating 10 may be deposited ontop of the buffer layer 22 instead of etched into the buffer layer 22,thereby resulting in a positive grating structure, as shown in FIG. 5.The depositing process may be performed by low-temperature sputtering,sol-gel solution techniques, spin-coating of a polymer film, or othertechniques known by one of ordinary skill in the art which accomplishsimilar results. The grating structure may also be fabricated bydepositing additional buffer through openings in a positive photoresistlayer.

A waveguide layer 24 is fabricated onto the etched buffer layer 22 byany of a number of suitable processes, such as spin coating (whichutilizes a mechanism for spinning the etched buffer layer 22 whileadding the waveguide solution) or dip coating. The thickness of thewaveguide layer 24 will be determined and controlled by the viscosity ofthe solution utilized to create the waveguide layer 24 and the speed ofspinning performed during fabrication. The significance of using suchprocesses as thin coating is that a perfectly planar surface is desiredso as to limit possible reflective interference in the waveguide layer24. Other processes of fabricating the waveguide 24 onto the bufferlayer 22 will be well known to those of ordinary skill in the art. Inthe first embodiment, the waveguide layer 24 is made of a polymermaterial such as polyphenylmethacrylate, with a refractive index ofapproximately 1.55 to 1.6.

The intensity of the light guided within the waveguide layer 24 istypically most intense at the center of the waveguide layer 24.Therefore, due to maximum guided light intensity being at the center ofthe waveguide layer 24, instead of at the bottom, which is where thediffraction grating 22 is located, the use of a negative grating linestructure is made possible due to the evanescent field of the guidedlight. The evanescent field is a low intensity portion of the guidedlight, which extends past the waveguide layer 24, into the buffer 22. Toprovide for optimal diffraction and transmission of the reflected lightby the diffraction grating 10, the buffer layer 22 has a relatively lowreflective index of approximately 1.47, as compared to the higherrefractive index of the waveguide layer 24, which is approximately 1.55to 1.6. Due to the absorbing characteristics of the substrate 20, anylight which extends past the buffer layer 22 is absorbed, preventingreflection into the waveguide layer 24 which may cause interference withnon-diffracted wavelengths. Therefore, the efficiency of the firstembodiment is dependent upon how much light is in the evanescent tail,as this governs the strength of the interaction with the diffractiongrating 10.

A clad layer 26 is fabricated to encompass the integrated-opticspectrometer, thereby providing protection and isolation of thewaveguide 24 from outside elements, such as, for example, dust.Preferably, the clad 26 is made of a low index polymer, such as Teflon®AF (Amorphus Fluoropolymer), which is manufactured by and madecommercially available from DuPont. Other materials which may beutilized for making the clad 26 include methacrylates, fluorinatedacrylates, or silicon dioxide. The diffracted index of the clad 26 isapproximately 1.35 to 1.4. Since the clad 26 has a lower refracted indexthan the waveguide 24, the reflected incident light is reflected off theclad 26 and prevented from escaping the waveguide 24.

A photodiode detector array 30, for example, an array of charge coupleddevices (CCDs), is attached to the top portion of the clad layer 26 foranalyzing the diffracted light. The purpose and composition of thephotodiode detector array 30 is further discussed herein with referenceto FIG. 6 and FIG. 7.

More than one diffraction grating 10 may be etched upon the buffer layer22. Therefore, as previously mentioned, the refractive indices of thedifferent layers act together to allow the diffraction of discretewavelengths from a reflected incident light by a first diffractiongrating and the transmission of non-diffracted wavelengths furtherthrough the waveguide 24 for further refraction by other successivediffraction gratings.

To maximize the efficiency of the integrated-optic spectrometer,diffraction of the reflected incident light is preferred to occur at thecenter of the waveguide which is where intensity of the light isstrongest. Therefore, a thicker sized waveguide is desired which alsoimproves the ease and efficiency of introducing the reflected incidentlight into the waveguide 24.

Referring to FIG. 3, a second embodiment of the present invention isshown which satisfies the need for thicker waveguides. In accordancewith the second embodiment of the present invention, a first bufferlayer 40 is fabricated upon the top layer of the substrate 20. Thisfabrication is accomplished by a process similar to the processdescribed in the first embodiment of the invention. A first waveguidelayer 42, preferably made of a high-index polymer or other material, isfabricated onto the first buffer layer 40, also by processes similar tothose described in the first embodiment of the invention.

A thin grating layer 44 is then fabricated onto the first waveguide 42using a positive grating line structure as depicted in FIG. 4. In apositive grating line structure, the thin grating layer 44 is createdwith the grating lines fabricated thereupon, instead of etchedtherefrom. As explained with reference to the first embodiment of theinvention, the thin grating layer 44 may be deposited upon the firstwaveguide layer 42 by low-temperature sputtering, sol-gel solutiontechniques, spin-coating, or other techniques understood by one ofordinary skill in the art which accomplish the same results. Also, thegrating structure may be fabricated by depositing additional bufferthrough openings in a positive photoresist layer. Similar to the firstembodiment, instead of utilizing a positive grating line structure, thethin grating layer 44 may be etched, thereby creating a negative gratingline structure.

A second waveguide layer 46 is fabricated onto the thin grating layer44, once again utilizing methods previously demonstrated in thefabrication of the waveguide layer 24 (FIG. 2) utilized in the firstembodiment. The second waveguide layer 46 provides a second path throughwhich the reflected incident light may pass and serves to thicken theoverall waveguide structure. Taken as a whole, and because the thingrating layer 44 is quite thin relative to the waveguide layers 42 and46, the whole device behaves like a thick continuous waveguide withembedded diffraction gratings.

A clad 26 is fabricated to encompass the integrated-optic spectrometer,thereby protecting the waveguide layers 42, 46 from outside obstructionsand interference.

Due to the specific positioning of the thin grating layer 44 in themiddle of the two waveguide layers 42, 46, the thin grating layer 44 islocated in the peak of the guided mode intensities, ensuring stronginteractions with the thin grating layer 44, as opposed to less stronginteraction in the first embodiment of the invention. Therefore, thesecond embodiment of the invention allows the thickness of the overallwaveguide to be increased several-fold, providing improved efficiency.

Finally, a photodiode detector array 30 is attached to the top portionof the clad 26 for analyzing the refracted light. The purpose andcomposition of the photodiode detector array 30 is further discussed inthe foregoing disclosure describing FIG. 6 and FIG. 7.

FIG. 6 illustrates diffraction of the reflected incident light into aphotodiode detector array 30. In accordance with the first and secondembodiments of the invention, the reflected incident light has discretewavelengths diffracted out of the waveguide by a first diffractiongrating. After being diffracted, the diffracted light then goes into thephotodiode detector array 30 through the clad 26, to be analyzed forparticular properties. The remaining wavelengths from the inputted lightsource are transmitted further within the waveguide 24 until furtherdiffracted by successive diffraction gratings. As previously disclosed,the diffraction grating and grating lines are formed to provide fordiffraction of the discrete wavelengths and optimal transmission ofnon-diffracted wavelengths.

The photodiode detector array 30 comprises a series of pixels whichrelate to specific wavelengths. These pixels are grouped and aligned toreceive specific wavelengths from the reflected incident light afterdiffraction from the diffraction gratings. These pixels may relate todifferent colors within the visual spectrum, thereby allowing theintegrated-optic spectrometer to analyze the color composition of thereflected incident light.

FIG. 7 better illustrates the diffraction of the inputted light source,in accordance with the first and second embodiments of the invention, aswell as redirection by the addition of a stand-off layer 50. Since theclad 26 does not effect the diffraction of the reflected incident light,it is not shown. The stand-off layer 50 is located between the waveguide24 and the clad 26. The standoff-layer 50 allows the refracted discretewavelengths to spread, so that they may fall directly on one or morepixels of the photodiode detector array 30.

Dead pixels 52 may be provided within the photodiode detector array 30so that there is a spread of, for example, approximately 5 to 7 pixelspositioned to receive the diffracted wavelengths from a respectivediffraction grating 10. Each of the pixels is also supplied with aunique set of wavelengths for evaluation. The dead pixels 52 preventlight refracted by the first grating from contaminating light refractedfrom a successive grating, and visa-versa.

FIG. 8 illustrates a top view of diffraction of the reflected incidentlight into the photodiode detector array 30 in accordance with the firstand second embodiments of the invention. As discussed with reference toFIG. 1, the diffraction grating 10 and grating lines 12 are designed todiffract light of selected wavelengths, at a specified angle within theplane of the waveguide 24. This may be performed by utilizing the 30°parallelogram shaped diffraction grating 10 having individual gratinglines at an angle of 45° to the direction of propagation of light withinthe waveguide 24.

FIG. 9 illustrates a top view of diffraction of the reflected incidentlight into a photodiode detector array 30 in accordance with the firstand second embodiments of the invention, utilizing diffraction gratings10 in the shape of a square or rectangle, with grating lines 12 at rightangles to the direction of propagation of light within the waveguide 24.Since the abovementioned diffraction grating/grating line combination isutilized the light which is coupled out of the waveguide 24 is in adirection which is more or less perpendicular to the plane of thewaveguide.

The foregoing has been illustrative of the features and principles ofthe present invention. Various changes or modifications to the inventionmay be apparent to those skilled in the art without departure from thespirit and scope of the invention. All such changes or modifications areintended to be included herein and within the scope of the invention.

What is claimed is:
 1. An integrated-optic spectrometer capable ofanalyzing light, comprising: a buffer layer created on the top layer ofa substrate; at least one diffraction grating formed on said bufferlayer, said diffraction grating being constructed of a series of gratinglines; a waveguide, fabricated onto said buffer layer capable of guidingsaid light within said integrated-optic spectrometer; and a photodiodedetector array, capable of analyzing discrete wavelengths, mounted ontop of said waveguide, said photodiode detector array containing aseries of pixels therein, wherein said diffraction grating is capable ofdiffracting discrete wavelengths out of said waveguide and into saidphotodiode detector array.
 2. The spectrometer of claim 1, wherein saiddiffraction grating is constructed as a four cornered shape with saidgrating lines at right angles to the direction of propagation of lightwithin said waveguide.
 3. The spectrometer of claim 1, wherein saiddiffraction grating is constructed as a 30 degree parallelogram withsaid individual grating lines at an angle of 45 degrees with thevertical plane of said waveguide.
 4. The spectrometer of claim 1,wherein said discrete wavelengths correspond to specific colors withinthe visual spectrum, wherein the wavelengths included in each color areout-coupled by each diffraction grating.
 5. The spectrometer of claim 1,wherein said diffraction grating is further defined by a positivegrating structure.
 6. The spectrometer of claim 1, wherein saiddiffraction grating is further defined by a negative grating structure.7. The spectrometer of claim 1, further comprising a clad, locatedbetween said waveguide and said photodiode detector array.
 8. Thespectrometer of claim 1, further comprising a standoff layer locatedbetween said waveguide and said photodiode detector array, wherein saidstandoff layer provides for spreading of said light after diffraction bysaid diffraction grating to match said pixels of said photodiodedetector array.
 9. An integrated-optic spectrometer capable of analyzinglight, comprising: a substrate, the top layer of said substrate beingoxidized to form a first buffer layer; a first waveguide layerfabricated onto said first buffer layer; a second buffer layerfabricated onto said first waveguide layer; at least one diffractiongrating formed on said second buffer layer, wherein said diffractiongrating is constructed of a series of grating lines; a second waveguidelayer, fabricated onto said second buffer layer; a photodiode detectorarray capable of analyzing discrete wavelengths, said photodiodedetector array being mounted on top of said second waveguide layer; anda clad encompassing said integrated-optic spectrometer, wherein saiddiffraction grating is capable of diffracting discrete wavelengths outof said second waveguide layer and into said photodiode detector array,while maximizing transmission of non-diffracted wavelengths.
 10. Thespectrometer of claim 9, wherein said diffraction grating is constructedas a 30 degree parallelogram with said grating lines at an angle of 45degrees with the vertical plane of said second polymer.
 11. Thespectrometer of claim 9, wherein said discrete wavelengths correspond tothe wavelengths which make specific colors within the visual spectrum,wherein a different color is out-coupled by each diffraction grating.12. The diffraction grating of claim 9, wherein said diffraction gratingis further defined by a positive grating structure.
 13. The diffractiongrating of claim 9, wherein said diffraction grating is further definedby a negative grating structure.
 14. A diffraction grating fordiffracting an inputted light source within a waveguide comprising: aseries of grating lines; wherein said grating lines have a peripheralboundary shaped to optimize the diffraction and transmission of saidinputted light source.
 15. The diffraction grating of claim 14, whereinsaid diffraction grating is further defined by a positive gratingstructure.
 16. The diffraction grating of claim 14, wherein saiddiffraction grating is further defined by a negative grating structure.17. The diffraction grating of claim 14, wherein said diffractiongrating is constructed as a four cornered shape with said series ofgrating lines at a right angle to the direction of propagation of saidlight within said waveguide.
 18. The diffraction grating of claim 14,wherein said diffraction grating is constructed as a 30 degreeparallelogram with said series of grating lines at an angle of 45degrees with the vertical plane of said waveguide.
 19. A method forcreating an integrated-optic spectrometer comprising the steps of:creating a first buffer layer on the top surface layer of a substrate;fabricating a first waveguide layer on said first buffer layer;fabricating a second buffer layer on the surface of said first waveguidelayer; forming at least one diffraction grating on the surface of saidsecond buffer layer; fabricating a second waveguide layer on the surfaceof said second buffer layer; mounting a photodiode detector array ontosaid second waveguide layer, wherein said photodiode detector array iscapable of analyzing discrete wavelengths; and encompassing saidintegrated-optic spectrometer with a clad.
 20. A means for analyzing thecomposition of reflected light utilizing an integrated-opticspectrometer comprising the steps of: receiving a reflected light sourcethrough a waveguide; and refracting discrete wavelengths from saidreflected light source via at least one diffraction grating, having aseries of diffraction lines, into a photodiode detector array foranalysis, while optimally transmitting non-refracted wavelengths furtherwithin said waveguide.